In the past, baro altitude and TAWS systems have provided critical information to pilots and flight crews. Avionics engineers have routinely endeavored to provide high integrity systems with associated high confidence levels for the information they provide. One approach has been to provide independent and dual redundant TAWS and baro altitude systems on each aircraft. Independent and redundant TAWS and baro altitude systems would typically have complete duplication of equipment that exists on-board the aircraft. For example, dual GPS receivers, dual terrain databases and dual database servers would be required for an independent dual redundant TAWS system.
While these independent and dual redundant systems may have many advantages in particular uses, they also have significant drawbacks. One common drawback of these designs is that they are very expensive. Another drawback of this approach at improving system integrity is the potential for common failure modes or common error sources. For example, for the TAWS, either the two TAWS systems are required to use two independently derived and supplied terrain databases, which are very expensive, or it is required to accept the potential for database errors which are common to each independent system. Additionally, errors in GPS positioning arising from sources other than the receivers on-board the aircraft are common to a redundant TAWS system. For the baro altitude sensor, dual identical systems have potential for common errors in the quality of current local baroset values available and to pilot error in entering such information.
Consequently, there exists a need for improved methods and apparatuses for improving the confidence levels in information provided by baro altitude and TAWS systems.